Esters of carbohydrates



Reissued Dec. 18, 1951 METHOD OF PRODUCING ETHERS AND ESTERS OF CARBOHYDRATES Jan Lolkema, Hoogezand, Netherlands; vested in the Attorney General of the United States No Drawing. Original No. 2,459,108, dated January 11, 1949, Serial No. 380,562, February 25, 1941. Application for reissue October 14, 1949, Serial No. 121,443. In the Netherlands January Section 3, Public Law 690, August 8, 1946 Patent expires January 23, 1960 9 Claims.

Matter enclosed in heavy brackets II appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

The invention relates to a method of producing ethers, esters and mixed ether-esters of carbohydrates, more particularly of starch in a dry form which are soluble in cold or in hot solution or pastes which can be used as adhesives. The production of the solid ethers in a dry condition from these reaction products is known likewise; for this purpose, however, comparatively laborious and expensive treatments were necessary, such as e. g. precipitation with alcohol, separation by dialysis or separation by adding inorganic salts with subsequent filtering, washing and drying. The products thus obtained were readily soluble in cold water, but only slightly soluble in hot water. Up to the present the said starch ethers have been but little used for technical purposes, which is partly due to the laborious methods of producing the same.

The production of [ethers of other carbohydrates and of esters of carbohydrates] starch esters is also known. Up to the present, however, they have also proved to be of small importance in actual practice.

The present invention relates to a method which renders it possible to produce in a very simple and economical manner from starch and other carbohydrates which may be made into a solution or paste by stirring them with a small proportion of water, ethers, esters and mixed ether-esters in the form of dry flakes or powders which are readily soluble in cold and/or hot water. This method consists in that a mixture of the carbohydrate with a limited quantity of water etherifying or esterifying agent and an alkaline substance either after the ethervification or esterification or in any desired stage of the said processes, is suddenly heated for a short time to a high temperature and pressed out or spread out to form [theirjlthin layers which are simultaneously dried. If gelatinizable carbohydrates are used as a starting material the reaction mixture is'preferably heated to a temperature above the gelatinizing temperaure.

The invention is chiefly important for the production of valuable products from starch or starch containing materials and starch derivatives, but it may also serve for the production of ethers and esters from other polysaccharides which likewise will produce viscous, sticky solutions both in cold and hot water.

The invention will now be described with regard to the production of starch ethers.

According to anembodiment of the invention the starch is' firstmixed with a small proportion of water (i. e. the proportion usual for the production of cold swelling starch) and with the chemicals required for etherification and, preferably after the etherification process has proceeded to a smaller or larger extent, subjected to the heating process described above.

This process may be carried out by stirring the starch e. g. with from /2-2 parts by weight of water and subsequently adding the quantity of the alkaline substance required for the reaction. As such e. g. alkali hydrates, salts having an alkaline reaction, ammonia or organic bases may be used. The addition of the said alkaline substances is necessary in most cases for eifecting thereaction with the etherifying agent.

The etherifying agent e. g. a dialkyl sulphate is now added to the said mixture while stirring. In order to accelerate the reaction, the reaction mixture may be heated, but since the reaction is exothermic, this generally will 'not be necessary and in some cases cooling is even advisable, in order to retard the reaction.

The mixture is'now suddenly heated during a short time to 'a high temperature and pressed or spread out to form thin layers which are simultaneously dried. This operation which is well known from' the manufacturing processes of cold swelling starch of which it forms an essential part, is preferably carried out by applying the mixture to rotating cylinders heated to a temperature of C. or above, which are positioned so that the mass is pressed into a thin layer. The starch will thereby be gelatinized in so far as. gelatinizing has not yet been effected by the alkali during the pre-treatment, and simultaneously dried, so that the material leaving the cylinders will consist of thin sheets or chips::which''may be. ground; if desired.

Beforethe mass is submitted to this treatment, a more or less advanced etheriflcation of the starch has already taken place; preferabl 'r' operations are carried out lmsuchwa-way that the reaction will be accomplished for-three-quar-- ters or more before the material is heated and dried on the cylinder.

During this latter treatment -'the-== etherification process will proceed, particularly, because of the fact that owing to the evaporationwotthe water the concentration ofthe'umeactedcpartof each component will increase very quickly,"

whereby the reaction will be considerably accelerated. It has accordingly, beenrfound. that the etheriflcaton process is completed within,

a short time and that in a few minutes a dry product of the desired degree of etherifica-tion is "obtained. The method .accordingw to the-in.- vention-thereiore renders it possibleqto utilize the etherifying agent as completely as possible in a very simple and inexpensive way.

Instead of immediately adding the entire quantity? of" alkaline substance to the starchwater' mixture; itr -is also possible: to add? the same entirely or partly together with the etherifying, agent.-' It is also:-possible-=ilrst to..mix the starch; with the 1 water and; thee. etherifying agent and-subsequently to :add: the required quantity -of1thealkaline substance.

Thevetherifying agent may-be diluted; if desired; with a: solventythiswsolvent, however,

must not have too: high a boiiingpoint; as it will have to evaporate again; during. the treatment on thewylinders;

[The alkyl groups furthermore; may have straight or .branchedrchains:whichrmay be inter- L mpted by-oxygen; nitrogen .or sulphur] [The starch1may also be: etherifled: with differentgroupsr In: that case theitstarc'h'. is reacted .withtworor morecethenfiyingn-agents which may be; added either. simultaneously" or. successively andr in any desiredgsequence ;.eitheivin immediate succession or at given intervals; Examples of such mixed starch ethers are thesmethyl-ethyl ether andrthe methyl hydroxyzlethylnthenil [When using" the term? ethers' of." carbohy- L drates? in the specification and J claims I only meamthose compounds in which onercarbon-atom does not contain more than one .hydroxy alkyl group andiitttherefore does notrlnclude the compounds-known. under the-namefiacetales" which are obtained by reacting aldehydes of ketones with hydroxy compounds,. era-g. the condensation products :of carbohydrateswithformaldehyde] .Elihe invention 'h-BJSibBeII described above for the production ofstarchl etherspbut the esters may alsobe preparedzin. azslmilarmanner, e; .g: by mix?- ing the-starch: with :a-zsmail. proportioni of "water and an alkaline substances subsequentlyadding an: acidchloride and after .thenreaction-has proceeded for a considerable part, heating; the mixture oncylindersin-the manner described above] [The esters used according-rte the invention are derived from'polybasic inorganic or-from monoor from pol-ybasicorganic-acids;v e: g; aliphatic or aromatic: acids, which 1 may also *contain one' or more 1015 the above mentionedsubstituents; The tenn:"esterifying agentswhen used inthespeciflcation and claimst-is not meant F to include-car;- bomdisulphide; which; although itis not'an esteritying agent in theusual sense, is capable: of form.-

ing xanthates when mixed with carbohydrates in the presence of alkali] [Furthermore it is also possible to produce mixed. eth'eresters by treating the starch both with etherifying and=esterifying'agents. If the addierg; with, acidsxsuch as sulphuric acid. In the etherifying: process. this acid will be partly or entirely liberated and for this reason it is generally necessary to. add. alkaline substances which combine..-with..the acid. It is, however, also possible to employ etherifying agents which do not produce acids,.such as the epoxy alkanes. Nevertheless it will be advantageous in this case also to addalkalinie substances as they will act as'catalysts' After the reaction has been completed; the-alkaline -s'ub stance may be partly on completely neutralized.

The alkyl groups whichmay be combined'with the starch by theetherifying process may be of "a varying character and theymay contain various substituents, e. g; one or'more hydroxyl groups, mercapto groups, rhodanide groups, halogen atoms, aminoor substituted amino groups, carboxylgroups or arylcarboxyl groupsor alkali salts respectively, alkaline earth salts orother salts or functional derivatives thereof,- suchas amides and substituted amides, sulphonic acid groups 'or aryl' :sulphonic acid groups, or salts or functional derivatives thereof and the like.

The alkyl groups furthermore may have straight or branched chains which" may biz-interrupted by-orygen, nitrogen or sulphur;

Thev starch may also-be. etherified with diflerent groups.- In that case the starch is reacted with twoor more etherifying agents which maybe added either simultaneously or successively and in anydesired sequence, either in immediate succession or at givenin-tervals. Examples of such mixed starch eth'ers are the methyl-ethyl ether and the'methyZ-hydrowyJZ ethyl ether;.

When'using the term ethers of carbohydrates" in the, specification and claims I only mean those compounds in which onecarbon atom does. not contain more than one hydroxy alkyl group and it therefore does not include thev compounds known under the name. of acetales which are obtained by reacting cldehydes of ketones. with hydrory compounds, 6. g. the condensation prodnets of carbohydrates with formaldehyde.

The invention has been described-above forihe production of'starch ethers, but the esters may also be prepared ina, similar manner, a. g.- by miringihe starchwitha-smull proportion: of water and an alkaline substance, subsequently adding tun-acid chloride andujter the reactionhas pro,- ceed-edfor a considerablcgpart; heating thermisiure on cylinders in: the manner described above.

The;esters used 'accordingiio the inventionare derived from polybasic. inorganic or from monoor from polybasic org'anicucids, e. g. aliphatic. or aromatic acids,- whfich'muy also contain ,oneror more of the above mentioned substituents: The term :esterifying agents when-used intthe. speci ficdtion and claims is not: meant to'include carbon disulphidawhich, although it is not an ester-ifyingugent in the. usual. sense; is capable of form-- addition of the esterifying agent occurs simultaneously with or after the addition of the etherifying agent, the esterifyin agent may react with free hydroxyl groups of the'starch as well as with certain groups, e. g. hydromyl or amino groups present in the etherifying agent either before or after etherification, or with both.

Similar derivatives as described above in connection with starch may also be produced from starch products as soluble starch, dextrine and the like, and from other carbohydrates, such as inullne, sugars, different kinds of gums, such as gum arabic, and the like, in so far as they can be made into a solution or paste by stirring the same with a small proportion of Water, and the products thus obtained are likewise soluble in cold and/or hot water. By a small proportion of water I mean the proportion generally used in the manufacture of cold swelling starch. Of course mixtures of different carbohydrates may also be used as starting materials.

The methods of production described above are extremely simple, practical and far less laborious than the methods used up to the present, which renders the final products less expensive.

When compared with the usual starch products used for technical purposes e. g. the well known soluble starches, cold swelling starches, dextrines and the like, the starch ethers and esters according to the invention have different properties, which give them special advantages for various purposes. Depending on the nature and/or the quantity of the etherifying or the esterifying agent used per unit of glucose, one obtains products which dissolved in water to a colloidal solution will show a great variation in regard to viscosity. The said viscous colloidal solutions are characterized by a gum-like character and a great and lasting transparency; they do not show retrogradation phenomena and in many cases will possess a better solubility and a strong adhesive power.

They furthermore have the advantage that they are not substantially attacked by microorganisms, so that practically no preservatives need be added to the adhesives produced from the said ethers and esters. Moreover the starch products thus produced will practically form no lumps when dissolved in cold water, a drawback which as is known, is generally inherent to cold swelling starch products.

I claim:

[1. The process of manufacturing adhesive alkyl ethers of a gelatinizable carbohydrate soluble in water to form a paste which comprises mixing the carbohydrate with an alkaline solution and an etherifying agent, spreading the mixture to form a thin layer and quickly heating the layer to a gelatinlzing temperature while evaporating the solution to accelerate the etherification] [2. The process of manufacturing adhesive alkyl ethers of starch soluble in water to form a paste which comprises mixing the starch with an alkaline solution and an etherifying agent, spreading the mixture to form a thin layer and quickly heating the layer to a gelatinizing temperature while evaporating the solution to accelerate the etherification] [3. The process of manufacturing adhesive alkyl ethers of starch soluble in water to form a paste which comprises mixing the starch with an alkaline solution and an etherifying agent, spreading the mixture to form a thin layer and quickly heating the layer to approximately 100 C. until dry.]

[4. The process of manufacturing adhesive alkylethers of starch soluble in water to form a paste which comprises mixing the starch with an alkali hydrate and an etherifying agent, spreading the mixture to form a thin layer and quickly heating the layer to approximately '100 C. until dry.]

[5; The process of manufacturing an adhesive ether of starch soluble in water to form a paste which comprises mixing the starch with an alkaline solution and diethyl sulphate, spreading the mixture to form a thin layer and quickly heating the layer to approximately C. until dry.

' [6. The process of manufacturing an adhesive etherof starch soluble in water to form a paste which comprises mixing the starch with an alkali hydrate and diethyl sulphatejspreading the mixture to form a thin layer and quickly heating the layer to approximately 100 C. until dry.]

['7. The process of manufacturing an adhesive ether of starch soluble in water to form a paste which comprises mixing the starch with an alkaline solution and an etherifying agent and quickly pressing a thin layer of the mixture between surfaces heated to 100 Ck] [8. The process of manufacturing an adhesive ether of starch soluble in water to formv a paste which comprises mixing the starch with an alkaline solution and an etherifying agent and quickly pressing a thin layer of the mixture between two rotating cylinders heated to 100 C] [9. The process of manufacturing an adhesive ether of starch soluble in water to form a paste which comprises mixing the starch with an alkaline solution and an etherifying agent, spreading the mixture to form a thin layer and completing the etherification by heating the layer to 100 C. until dry.]

10. The process of manufacturing water soluble adhesive derivatives of polysaccharides, which in unreacted condition are soluble in water to form a paste which comprises mixing the polysaccharide with an alkaline solution and a reagent of the group consisting of etherifying organic esters of inorganic acids, etherifying epoxyalkanes and esterijying agents derived from organic acids, spreading the reaction mixture to form a thin layer and quickly heating the layer to at least 100 0., while evaporating the solution.

11. The process of manufacturing water soluble adhesive derivatives of gelatinizable polysaccharides, which in unreacted condition, are soluble in water to form a paste which comprises mixing the gelatinieable polysaccharide with an alkaline solution and a reagent of the group consisting of etherifying agents and etherifying organic esters of inorganic acids, etherifying epoxyalkanes derived from organic acids, spreading the reaction mixture to form a thin layer and quickly heating the layer to at least 100 0., while evaporating the solution.

12. The process of manufacturing water soluble adhesive starch derivatives which comprises mixing the starch with an alkaline solution and a reagent of the group consisting of etherifying organic esters of inorganic acids, etherifying epomyalkanes and esterifying agents derived from organic acids, spreading the reaction mixture to jformia'thinslayer qand qu icldu heatingithet-layer-to saw-reagent: .o'f the grcup con-sisting gofsetherifying at- 'least$100icfliuntil'clry. organic esters of inorganic acids, vetherz'jfying :13. Til/8717700888 of manufacturing water -s0laBZJOJXI/(ZUCLZTLBS :and esterifying yagents :derived :ubleadhesive starc-hR-derivativeswhich comprises from organic acids and quickly Z71'68 ing. =a.-thin mixing the starch with an alkali hydrate anda .5 slayer of the reaction mixture-between rotating reagent of the group consisting of etherifying orccylinders heated to at least 100 C.

i'ganicesters'of. inorganic acids, etherifying epoicy- 118. The process of manufacturing waterflsolia-lka-nes and-esterifying agents derived 3 from" or- -uble adhesive starch derivatives whichrcomprises s'ganic acids, spreading the'reaction mixture to umi'aringthe starch with an alkaline soiutionaand f a ay and quicklyheating he ye fiflva 'reagentiopthe group consisting .of etherifying tto atr least 100 C. until dry. torganic aesters :Of inorganic acids, :etherifying WO SS :01 anufa uri g wa -S0 -epo':vyalkanes and esterifying agents derived uble adhesive starch derivatives whichcomprises from organic acids,;spreadingthe reaction mixmixing thestarchwith an alkaline-solution and tureto form athin layerzand completing :the 'diethyl. sulphate,- spreading the reactiontmixture15-etheriflcation byheating-ihe layer 'to at least to formathin layer and quickly heating thelayer 1100" C'.-;unt.il1,dry.

to =at least 1-00C'. until dry. JANLOL M .525. The 1 process of manufacturing water solz-uble adhesive: starch-derivatives. which comprises :REFERENCES CITED mining the starch with an alkali hydrate and \di- 320 The Ffollow-mgrmfermmes are of recomzinxthe eethylssulphate; spreading the reaction-mixture to True of this pabentioriythe original patent: v ijormca thin layer and quickly heating .theslayer Fto atwleast=100- 0. until dry. UNITED STATES PATENTS 1 6.=The'process of manufacturing water soli b N t sable-adhesive starch -derivatives-which comprises 25 11505365 =Huber May 12, 1931 mixing the starchwith an alkalinesolutionand 1,979,257 Giesicke Nov. 6,4934 va re n of e group consisting-of e h rifvin 2,116,867 Kreimeieretal.; 'May;10,-1938 uorganic esters of inorganic .acids, -etherifying 2 143,951 M ,x e11 Feb, 28, ,1939 epozcyallcanesand'esterifying agents. derived from 2,222,872 Luick :Nov.;26, 1940 prganicacids :and quickly pressing athin layer 1 :40 2,288,200 :Meyer 1 JuneBO, 1942 1?; 21: 2 glfgtctiigg igwture betweensurfaces heated OTHERTREFERENCES I -.17. The process of manufacturing water :sol- American Dyestuff "Reporter, .June 19, 11933,

auble adhesive starch derivatives which comprises .,p. 379,.by vHall-Huntress. Problemscin Organic mixing thestarchtwith an alkaline'solution .and 35 schemistry pagefll, McGraweI-Iill (193,8). 

